The organic light-emitting display device has drawn lots of attention due to its advantages such as low power consumption, high brightness, low cost, wide angle of view, fast response and so on, and has been widely used in the technical field of organic light-emitting.
The Organic Light Emitting Diode (OLED) is a light emitting device that is used commonly in the organic light-emitting field. Currently, OLED can be classified into a passive driving type and an active driving type, that is, a direct addressing type and a Thin Film Transistor (TFT) matrix addressing type, according to its driving manner. The active driving OLED is also referred to as an Active Matrix OLED (AMOLED), wherein the light-emitting devices in each pixel unit are driven to emit light by a pixel circuit and a power line for loading a direct current (DC) power source voltage signal (Vdd or Vss).
Referring to FIG. 1, it is a structural schematic diagram of a pixel circuit for driving a light emitting device to emit light in the prior art. Taking N type driving transistor as an example, the pixel circuit comprises a driving transistor T1, a capacitor C1, and a switching transistor T2. A first terminal of the capacitor C1 is connected to the gate of the driving transistor T1, and a second terminal of the capacitor C1 is connected with a low level reference voltage source Vss. The drain of the switching transistor T2 is connected to the gate of the driving transistor T1, the gate of the switching transistor T2 is connected with a gate signal source VScan, and the source of the switching transistor T2 is connected with a data signal source VData. The source of the driving transistor T1 is connected with a high level reference voltage source VDD, the drain of the driving transistor T1 is connected to the anode of the light emitting device D1, and the cathode of the light emitting device D1 is connected with a low level reference voltage source Vss.
During a period in which one frame of picture is displayed, before the light emitting device D1 is driven to emit light, the gate signal source VScan outputs a voltage signal to turn on the switching transistor T2, the data signal source Vdata is connected to a branch where the capacitor C1 is located, and the data signal source VData outputs a data signal to be applied to the first terminal of the capacitor C1 to charge the capacitor C1; when the light emitting device D1 is driven to emit light, the gate signal source VScan outputs a voltage signal to turn off the switching transistor T2, and the data signal source VData is disconnected with the branch where the capacitor C1 is located, such that the capacitor C1 is discharged to drive the light emitting device D1 to emit light.
The pixel circuit provided in the prior art comprises only one driving transistor and a light emitting device connected to the driving transistor. During a period in which one frame of picture is displayed, the driving transistor in the pixel circuit drives the light emitting device to emit light. The AMOLED display drives the OLED to emit light by DC driving. The electric field corresponding to a long-term DC driving voltage would polarize ions inside the OLED, such that a built-in electric field is formed in the OLED, thus increasing the threshold voltage of the OLED, decreasing the light-emitting efficiency of the OLED a lot, and shortening the lifespan of the OLED. The lifespan is an important factor limiting the wide application of the organic light-emitting display, especially of the organic light-emitting display with a large size and high intensity.